The purpose of these studies will be to define the components of the immune response associated with immune suppression of tumor growth. The components of the immune response required for the in vitro generation of cytotoxic lymphocytes to syngeneic Gross virus-induced lymphoma cells is currently being evaluated. Cytotoxic cells generated in vitro are also being evaluated for their ability to suppress tumor growth in vivo. Whether in vitro generated cytotoxic lymphocytes directly mediate tumor cell suppression in vivo, or recruit cooperating host cells to allow for tumor growth suppression, is also being evaluated. The effect of BCG on the generation of effector lymphocytes will be determined. Additionally, the biological importance of unique versus common tumor-specific transplantation antigens expressed by polyoma virus-induced tumors is being evaluated.